Cal. Food & Agric. Code § 58351

Any contract which is made for the purpose of injuring competitors and destroying competition under which the seller of any agricultural product agrees to pay or allow any brokerage charge, rebate, discount, or other credit, except an allowance for variation in quality, condition, or quantity, or any other form of compensation or credit by a seller to a buyer, or to an agent, employee, subsidiary, or affiliate of a buyer that buys to sell at retail and which is not paid, given, or allowed in like circumstances to all other buyers or to the agents, employees, subsidiaries or affiliates of other buyers, whether the same is paid or allowed directly or indirectly, is hereby declared to be against public policy and void.